Add handler for Move activity (#9629)

app/lib/activitypub/activity.rb

@@ -50,6 +50,8 @@ class ActivityPub::Activity
         ActivityPub::Activity::Add
       when 'Remove'
         ActivityPub::Activity::Remove
+      when 'Move'
+        ActivityPub::Activity::Move
       end
     end
   end

app/lib/activitypub/activity/follow.rb

@@ -6,7 +6,7 @@ class ActivityPub::Activity::Follow < ActivityPub::Activity
 
     return if target_account.nil? || !target_account.local? || delete_arrived_first?(@json['id']) || @account.requested?(target_account)
 
-    if target_account.blocking?(@account) || target_account.domain_blocking?(@account.domain)
+    if target_account.blocking?(@account) || target_account.domain_blocking?(@account.domain) || target_account.moved?
       reject_follow_request!(target_account)
       return
     end

app/lib/activitypub/activity/move.rb

@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+class ActivityPub::Activity::Move < ActivityPub::Activity
+  PROCESSING_COOLDOWN = 7.days.seconds
+
+  def perform
+    return if origin_account.uri != object_uri || processed?
+
+    mark_as_processing!
+
+    target_account = ActivityPub::FetchRemoteAccountService.new.call(target_uri)
+
+    return if target_account.nil? || !target_account.also_known_as.include?(origin_account.uri)
+
+    # In case for some reason we didn't have a redirect for the profile already, set it
+    origin_account.update(moved_to_account: target_account) if origin_account.moved_to_account_id.nil?
+
+    # Initiate a re-follow for each follower
+    origin_account.followers.local.select(:id).find_in_batches do |follower_accounts|
+      UnfollowFollowWorker.push_bulk(follower_accounts.map(&:id)) do |follower_account_id|
+        [follower_account_id, origin_account.id, target_account.id]
+      end
+    end
+  end
+
+  private
+
+  def origin_account
+    @account
+  end
+
+  def target_uri
+    value_or_id(@json['target'])
+  end
+
+  def processed?
+    redis.exists("move_in_progress:#{@account.id}")
+  end
+
+  def mark_as_processing!
+    redis.setex("move_in_progress:#{@account.id}", PROCESSING_COOLDOWN, true)
+  end
+end

app/lib/activitypub/adapter.rb

@@ -10,6 +10,7 @@ class ActivityPub::Adapter < ActiveModelSerializers::Adapter::Base
         'manuallyApprovesFollowers' => 'as:manuallyApprovesFollowers',
         'sensitive'                 => 'as:sensitive',
         'movedTo'                   => { '@id' => 'as:movedTo', '@type' => '@id' },
+        'alsoKnownAs'               => { '@id' => 'as:alsoKnownAs', '@type' => '@id' },
         'Hashtag'                   => 'as:Hashtag',
         'ostatus'                   => 'http://ostatus.org#',
         'atomUri'                   => 'ostatus:atomUri',